Evidence for evolution

Nature of Science

• Science is:

  • guided by natural law (the laws of physics and chemistry)

  • explained by reference to natural law

  • testable

  • tentative

  • falsifiable

Principle of superposition

Fossil found in the rock layers at the bottom of a sequence of strata are older than fossils found in strata on top

Stratigraphy

Study of rock layers

Comparative stratigraphy

Compares and correlates rock strata sequences from two or more areas by matching strata on the type of sediment and type of fossils

Index fossils

Preserved remains of organisms that were widely distributed but present on Earth for a limited period of time

Intermediate forms

Fossils that show transitional features of two distinct groups of organisms

Comparative anatomy

The study of similarities and differences in the anatomy of different species

Homologies

Similar characteristics shared by two different organisms because they were inherited from a common ancestor

Analogies

Similar characteristics shared by two different organisms because of convergent evolution

Phylogenetic constraint

Evolution is constrained by ancestry

Comparative embryology

Closely related species go through similar stages of development

Vestigial organs

Structures that have reduced in size to conserve energy with little or no function in its present day form

Homologous structures

Structures with a similar design but modified for a particular function

Atavistic features

Where an ancestral genetic trait appears in a present day form after having been lost through evolutionary change in previous generations

Analogous features

Similar features that have evolved independently through similar environmental selection pressures (convergent evolution)

Homoplasy

Unrelated structures that look alike

Adaptive radiation

Evolution of several ecologically diverse species from a common ancestral species

Artificial selection

The process by which humans selectively breed organisms for specific desired traits

Natural selection

Organisms that have adapted to their environment are more likely to succeed and reach reproductive age to pass on their genes for the next generations

Evolution

Change in a population over generations

Cladogenesis

A division of a single lineage into two lineages

Anagenesis

Evolution within a single lineage (species becoming more complex over time)

Evolutionary stability

Organisms that have remain morphologically unchanged over generations due to a stable selection pressure